* initial impl of Bars, Staircase, Smooth modes
* fix fillTo for staircase and smooth paths
* fix pointSize
* [bars] adjust gap factor & reduce bar width to include stroke width. remove rounding to favor gap & width uniformity over edge crispness.
* remove line path fallback for too-dense data
* "Auto" points mode implies "Never" for Bars
* slightly reduce x axis tick density
* fix bars height calc, make bars crisp again.
* [bars] don't use hard-coded 'x' scale key
* refactor catmullRomFitting() to accept x & y coord arrays. restrict to processing only visible data range.
* move path building functions to own file
* export typed functions
Co-authored-by: Ryan McKinley <ryantxu@gmail.com>
